12 October 2017

OFDM modem 12+12 tones 48Bd (Marconi 25-tones)

Probably a simplex transmission heard on 6246.5 KHz/USB. Although the SNR is poor, it's possible to see a central un-modulated tone a + 1500Hz that splits the signal in two identical parts which I analyzed separately. The results show an OFDM modulation of 12 + 12 tones at a rate of 48 symbols/sec; the on-air constellation seems to be QPSK on each channel.